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Message-Id: <20231124075953.1932764-6-yukuai1@huaweicloud.com>
Date: Fri, 24 Nov 2023 15:59:52 +0800
From: Yu Kuai <yukuai1@...weicloud.com>
To: song@...nel.org, yukuai3@...wei.com, xni@...hat.com
Cc: linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
yukuai1@...weicloud.com, yi.zhang@...wei.com, yangerkun@...wei.com
Subject: [PATCH v2 5/6] md: fix stopping sync thread
From: Yu Kuai <yukuai3@...wei.com>
Currently sync thread is stopped from multiple contex:
- idle_sync_thread
- frozen_sync_thread
- __md_stop_writes
- md_set_readonly
- do_md_stop
And there are some problems:
1) sync_work is flushed while reconfig_mutex is grabbed, this can
deadlock because the work function will grab reconfig_mutex as well.
2) md_reap_sync_thread() can't be called directly while md_do_sync() is
not finished yet, for example, commit 130443d60b1b ("md: refactor
idle/frozen_sync_thread() to fix deadlock").
3) If MD_RECOVERY_RUNNING is not set, there is no need to stop
sync_thread at all because sync_thread must not be registered.
Factor out a helper prepare_to_stop_sync_thread(), so that above contex
will behave the same. Fix 1) by flushing sync_work after reconfig_mutex
is released, before waiting for sync_thread to be done; Fix 2) bt
letting daemon thread to unregister sync_thread; Fix 3) by always
checking MD_RECOVERY_RUNNING first.
Fixes: db5e653d7c9f ("md: delay choosing sync action to md_start_sync()")
Signed-off-by: Yu Kuai <yukuai3@...wei.com>
---
drivers/md/md.c | 96 ++++++++++++++++++++++++-------------------------
1 file changed, 46 insertions(+), 50 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 5af67748e53e..fb8a7d1eebee 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -4846,26 +4846,9 @@ action_show(struct mddev *mddev, char *page)
return sprintf(page, "%s\n", type);
}
-static void stop_sync_thread(struct mddev *mddev)
+static void prepare_to_stop_sync_thread(struct mddev *mddev)
+ __releases(&mddev->reconfig_mutex)
{
- if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- return;
-
- if (mddev_lock(mddev))
- return;
-
- /*
- * Check again in case MD_RECOVERY_RUNNING is cleared before lock is
- * held.
- */
- if (!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
- mddev_unlock(mddev);
- return;
- }
-
- if (work_pending(&mddev->sync_work))
- flush_workqueue(md_misc_wq);
-
set_bit(MD_RECOVERY_INTR, &mddev->recovery);
/*
* Thread might be blocked waiting for metadata update which will now
@@ -4874,6 +4857,8 @@ static void stop_sync_thread(struct mddev *mddev)
md_wakeup_thread_directly(mddev->sync_thread);
mddev_unlock(mddev);
+ if (work_pending(&mddev->sync_work))
+ flush_work(&mddev->sync_work);
}
static void idle_sync_thread(struct mddev *mddev)
@@ -4882,10 +4867,20 @@ static void idle_sync_thread(struct mddev *mddev)
mutex_lock(&mddev->sync_mutex);
clear_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- stop_sync_thread(mddev);
- wait_event(resync_wait, sync_seq != atomic_read(&mddev->sync_seq) ||
+ if (mddev_lock(mddev)) {
+ mutex_unlock(&mddev->sync_mutex);
+ return;
+ }
+
+ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+ prepare_to_stop_sync_thread(mddev);
+ wait_event(resync_wait,
+ sync_seq != atomic_read(&mddev->sync_seq) ||
!test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+ } else {
+ mddev_unlock(mddev);
+ }
mutex_unlock(&mddev->sync_mutex);
}
@@ -4894,9 +4889,19 @@ static void frozen_sync_thread(struct mddev *mddev)
{
mutex_lock(&mddev->sync_mutex);
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- stop_sync_thread(mddev);
- wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+ if (mddev_lock(mddev)) {
+ mutex_unlock(&mddev->sync_mutex);
+ return;
+ }
+
+ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+ prepare_to_stop_sync_thread(mddev);
+ wait_event(resync_wait,
+ !test_bit(MD_RECOVERY_RUNNING, &mddev->recovery));
+ } else {
+ mddev_unlock(mddev);
+ }
mutex_unlock(&mddev->sync_mutex);
}
@@ -6270,11 +6275,11 @@ static void md_clean(struct mddev *mddev)
static void __md_stop_writes(struct mddev *mddev)
{
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
- if (work_pending(&mddev->sync_work))
- flush_workqueue(md_misc_wq);
- if (mddev->sync_thread) {
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
- md_reap_sync_thread(mddev);
+ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+ prepare_to_stop_sync_thread(mddev);
+ wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
+ &mddev->recovery));
+ mddev_lock_nointr(mddev);
}
del_timer_sync(&mddev->safemode_timer);
@@ -6367,18 +6372,15 @@ static int md_set_readonly(struct mddev *mddev, struct block_device *bdev)
did_freeze = 1;
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
}
- if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
- /*
- * Thread might be blocked waiting for metadata update which will now
- * never happen
- */
- md_wakeup_thread_directly(mddev->sync_thread);
+ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+ prepare_to_stop_sync_thread(mddev);
+ wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
+ &mddev->recovery));
+ } else {
+ mddev_unlock(mddev);
+ }
- mddev_unlock(mddev);
- wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
- &mddev->recovery));
wait_event(mddev->sb_wait,
!test_bit(MD_SB_CHANGE_PENDING, &mddev->sb_flags));
mddev_lock_nointr(mddev);
@@ -6429,19 +6431,13 @@ static int do_md_stop(struct mddev *mddev, int mode,
did_freeze = 1;
set_bit(MD_RECOVERY_FROZEN, &mddev->recovery);
}
- if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery))
- set_bit(MD_RECOVERY_INTR, &mddev->recovery);
-
- /*
- * Thread might be blocked waiting for metadata update which will now
- * never happen
- */
- md_wakeup_thread_directly(mddev->sync_thread);
- mddev_unlock(mddev);
- wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
- &mddev->recovery));
- mddev_lock_nointr(mddev);
+ if (test_bit(MD_RECOVERY_RUNNING, &mddev->recovery)) {
+ prepare_to_stop_sync_thread(mddev);
+ wait_event(resync_wait, !test_bit(MD_RECOVERY_RUNNING,
+ &mddev->recovery));
+ mddev_lock_nointr(mddev);
+ }
mutex_lock(&mddev->open_mutex);
if ((mddev->pers && atomic_read(&mddev->openers) > !!bdev) ||
--
2.39.2
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